A factory for manufacturing semiconductor substrates (e.g., patterned or unpatterned wafers) is conventionally known as a “FAB.” Within a FAB, an overhead transport mechanism may transport semiconductor wafers in what is known as a wafer carrier (e.g., a sealed pod, a cassette, a container, etc.) between various processing systems, wherein a wafer carrier is placed on a mechanism known as a loadport (i.e., a mechanism or location which receives and supports a wafer carrier at a given tool). Certain loadports referred to herein as fabrication tool loadports, support a wafer carrier while wafers are extracted from the wafer carrier and transported into a processing system coupled thereto. Others simply receive a wafer carrier within a storage buffer, where the wafer carrier is stored for subsequent transport to a fabrication tool loadport.
Typically, wafer carriers are received in a storage buffer via an elevated or overhead loadport that receives wafer carriers from an overhead transport mechanism. Thereafter a storage buffer robot may transfer the wafer carrier from the overhead loadport to another storage shelf or to a fabrication tool loadport or to a conventional SEMI Standard E15 loadport that exchanges wafer carriers with an overhead transport mechanism. To lower the wafer carrier from an overhead transport mechanism to an overhead loadport, a robot capable of multi-axis movement may be employed, etc. The complex multi-axis movement required by such a loader robot in order to transfer a wafer carrier between the overhead transfer mechanism and the overhead loadport increases equipment expense and reduces equipment reliability.
Also, conventionally wafer carriers have kinematic mounts (i.e., mechanical couplings used to align a wafer carrier on a platform, such as a loadport), which engage corresponding kinematic mount locations on a loadport. Thus, the loader robot must be tightly toleranced to accurately position the wafer carrier on the loadport such that the wafer carrier's kinematic mounts may engage the loadport's kinematic mount locations. Such tight tolerance requirements may increase equipment costs while reducing equipment throughput.
Accordingly, there is a need for an improved system that may transfer wafer carriers between an overhead transport mechanism and a loadport.